Production of organic phosphonyl halide



2,882,315 PRODUCTION OF ORGANIC PHOSPHONYL HALIDE Herbert J. Passino, Englewood, N.J., assignor to The M. W. Kellogg Company, Jersey City, N.J., a corporation of Delaware No Drawing. Application May 10, 1956 Serial No. 584,410

20 Claims. (Cl. 260 -543) This invention relates to a method for the manufacture of an organic phosphonyl difiuoride. In one aspect the invention relates to the production of alkyl and cycloalkyl phosphonyl difluorides. In another more particular aspect the invention relates to the production of methane phosphonyl difluoride.

This application is a continuation-in-part of my prior and copending application Serial No. 200,485, filed December 12, 1950, now abandoned.

Methane phosphonyl difluoride is a known gaseous compound and is an exceedingly important compound. Prior to the present invention this compound has been produced by devious and round about methods involving numerous chemical and mechanical steps. The following equations indicate the presently proposed stepwise method for producing methane phosphonyl difluoride:

(1), 6CH3OH 2PO1; 2(CH3O);POH 20152301 om-i on 2CHai OH 0 CHsOCHa CH: CHr-ILOH CHs-P OH H O 35001: ZCHaPCh 350: ZHCl CH3-=-P OH It is an object of this invention to provide a cheap and direct method for producing an organic phosphonyl difluoride.

Another object of this invention is to provide a method for producing methane phosphonyl difluoride in relatively high yields with high selectivity.

Still another object is to produce an organic phosphonyl halide with the minimum of by-products and with the maximum utilization of reactants.

Various other objects and advantages of the present invention will become apparent to those skilled in the art from the accompanying description and disclosure.

In'accor'dance with this invention an organic phosphonyl halide having the general formula:

where R is an organic radical, preferably an alkyl or ice cycloalkyl radical including the substituted radicals, such as an aralkyl radical or a halogen substituted alkyl or cycloalkyl radical, and X is a halogen atom of an atomic] weight not greater than and the Xs may be the same or different halogen atoms, is produced by directly reacting a phosphorus halide, preferably the trihalide, at

an elevated temperature with an organic compound of the formula: R-OR in which R is an organic radical and is the same as the R of the general formula for the organic phosphonyl halide, and R is a radical containing an organic group. Mixtures of such organic compounds may be reacted with the phosphorus halide without departing from the scope of this invention.

Various phosphorus halides in which the halogen atoms I are those having an atomic weight not greater than 80 may be employed. The phosphorus halides to be em ployed include phosphorous trifluoride, phosphorus trichloride, phosphorus tribromide, phosphorus pentafiuoride, and the mixed phosphorus halides such as fluoro phosphorous dichloride, difiuoro phosphorous chloride,

fiuorochloro phosphorous bromide, dichloro phosphorous bromide, difiuoro phosphorus trichloride and difiuoro phosphorous bromide. Of these phosphorus halides, the

trivalent phosphorous halides are preferred. The particular phosphorus halide employed depends upon the ultimate product desired. When producing an organic phosphonyl difluoride, a difiuoro phosphorus halide such as phosphorous trifluoride (Plis preferred.

The organic compounds of the formula R--O--R tobe reacted with the phosphorus halide include the ethers, esters, acetals and ketals and are preferably those compounds in which R is an alkyl ar cycloalkyl radical having not more than eight carbon atoms and in which R is an organic radical having not more than eight carbon atoms. The R radical has a continuous carbon skeleton,

. i.e. it is a radical in which the base carbon atoms are bonded directly to one another, the carbon atoms of the' carbon skeleton being singly bonded to various monovalent groups such as hydrogen, halogen, nitro and cyano groups. R may be of the same class and type of radicals as R, or R may be of a different class of radicals. Thus, H

R may also be a radical having a continuous carbon skeleton in which the carbon atoms are singly bonded to various monovalent groups such as hydrogen, halogen, nitro and cyano radicals. When R and R are of the same class of radicals, R and R may be the same radicalas in the simple symmetrical ethers, or R and R may be different radicals as in the simple unsymmetrical. I ethers. When R and R are of the same class of radicals as in the simple ethers, a mixture of organic phosphonyl halides is usually obtained in which the groups corresponding to the R and R groups of the starting material are bonded to phosphorous.

As indicated above, the definition of R includes radicals which are of a difierent class than those defined for R. Thus, R also may be an organic radical in which-- two of its base carbon atoms are separated by an atom of oxygen as in the polyethers, acetals and 'ketals and certain types of esters as the ortho esters. R also may contain one or more carbon atoms which are doubly bonded to oxygen as in the monoesters and polyesters which contain a carbonyl group (0 0).

The preferred organic ethers are selected from the group consisting of the alkyl and cycloalkyl ethers including the substituted alkyl ethers such as aralkyl ethers.

, Examples of ethers are the simple symmetrical ethers such:

as dimethyl ether, diethyl ether, dipropyl ether, di-n-butyl ether, diisoamyl ether, dihexyl ether, dioctyl ether, di cyclohexyl ether, and dibenzylether. Such symmetrical ethers are the preferred type of ether reactant to be em ployed since they result in a maximum yield of the corresgg spending organic phosphonyl difluoride. Also to be em- Patented Apmll, a

ployed are the unsymmetrical of."the-main organic phosphonyl dihalide produced as :a.

productof'the process. Thus, when an unsymmetrical methylether such as methyl propyl ether is interacted with phosphorus trifiuoride,,for example, a mixture of products is obtained, one component of which is methane phosphonyl 'difiuoride.

Various substituted .ethersmay also be. employed, such.

as the halo, nitro andcyanosubstituted ethers, for. example; beta,bcta'-'dichloro. diethyl. ether; chloromethyl ether; bcta,betai-oxy diproprionitrile; and Z-nitropropyl methyl ether. onlyoneetherlinkage, poly ethers, such as polyoxymetha ylenfi, polyoxyethylene. and. polyoxypropylene alcohols maybe employed, in. this .invention.

Examplesof the esters include the mono esters, the polyesters and .the ortho esters.- Preferred mono esters are: methyl formate, methyl acetate, butyl acetate, phenyl acetate, benzyl acetate andrnethyl proprionate. Suitable orth'o esters include trimethyl ortho formate, trimethyl ortho acetate and trimethyl ortho benzoate. Examples of polyesters are: dimethyl oxalate, dimethyl phthalate and dimethyl'adipate. Other esters include the polyesters of "inorganic acids, suchas dimethyl sulfate, diethyl sulfate, trimethyl b'orate, tributyl borate andtriethyl phosphate. Such vesters can. beformed by reacting an acid withan alcohol according to general esterification principles. When employing an ester as a reactant in accordance with this invention, the organic radical derived from the alcohol used to form the ester, preferentially becomes bonded to phosphorus andbecomes an element of .the main product of the reaction. For example, when a mono-ester. having the formula R'O'('5"R"* is*reacted with-PF,-', as. described herein, the R group of'th'e-alcohol portion of the ester becomes attached to phosphorus to produce as a main product of reaction wherein-Kin the ester reactant and the product are the sameand are as above-defined: Thecarbonyl-containing portion OR. O ris employed as a-reactant, the R"OCH radical represents. the R.. radical of the R.O -R reactant and the'R group. preferentially becomes: bonded to phosphorus; Thus; .fonexample; when .dimethyl formal is interacted withphosphorus trifluoride as described here-v in; the main product of reaction is methane phosphonyl.

Itistead ,of using simple ethers containing When an acetal' Examples of ketalsv for use in this invention are: di-v methyl ketal of acetone and cyclohexanone. When such methyl hotels are employed, the main product of reaction is a methane phosphonyl dihalide, the reaction taking place in much the same manner as that described above for the esters and acetals.

A typical. equation representing. the reaction of this invention is shown below:

where R and'R cussed.

The above reaction-is carried out-preferably at a temperature above about C. and below the decomposition temperature .of the reactants. Generallythe temperature will be below about 400. C; Thereactionisprefen ably carried outin the liquidphaseand'this is accorm. plished by employingsufiicient pressure to. maintain the. reactants-in liquid phase condition in the reaction. zone. at the temperature employed. The processis preferably carried out at an elevated pressure rangingfromab'out 300 to about 3500.p.s.i. absolute or higher. and 'is usually. affected at a pressure between about 500 and. 3,000..p .s.i.. In order to obtain the desired elevated pressure, thereaction zone may be pressured with an inert gas-suchas nitrogen until the desired pressure is obtained. Con? veniently, the reaction is carried out under autogenous conditions of .pressure in a suitable closed reaction vessel such as a steel bomb. The preferred temperature range for liquid'phase operations at elevated pressures .isa temperature between about 200 and about 350 C.

Methane phosphonyl difiuoride-is-produced by thefol-. lowing reaction under the above preferred reaction conditions:

areorganic radicals;;as previously diswherein CH OR is used to represent amethyl ether, a methyl ester, a methyl acetal, and a methyl ketal and wherein the methyl group becomes bonded to phosphorus to form the main organic phosphonyl halide product of the process. The methane phosphonyl difluoride is separated from the reactionmixture by distillation.

The reaction may be carried out with or without the presence of catalysts, promoters or initiators. Catalysts which are beneficial in affecting the reaction are those of the Friedel-Crafts type, such as aluminum chloride, aluminum bromide, stannic chloride, trifluoride and hydrogen fluoride. employed, preferably it is employed 0.01 mole to about 2 moles per mole of the difiuoro phosphorus halide. The use ofa Friedel-Crafts catalyst such as aluminum chloride leadsto higher yields of desired product as compared to the yields obtained under the same reaction conditions when. a. catalyst'is not employed. Another advantagederivedfrom the use. of such a catalyst is that it allowsfor the production of: desired. product at a temperature which is from about 10 degrees to about 25 degrees lower than the tempera. ture required to obtain comparable yields ofproductinthe absence of a catalyst.

The ratio of difiuorophosphorushalide and organic reactant may bevaried'over. relatively wide. limits v.but it. is preferable to employ arslight excess of the .organic reactant. Similarly, ,the time. of reaction mayvary over? relatively wide limits, such as one minute to about 12 hours, with a reaction time of at least 0.5 hour being preferred.

When .a catalyst is in an amount from zinc chloride, boron;-

It is postulated, without limiting the invention, however, that the reaction mechanism may be written as follows:

In view of the above concept, it is, therefore, desirable to initiate the reaction with a small amount of an alkyl halide which acts as an initiator according to the above equations.

The organic fluoride (R'F) formed by the reaction may be utilized in the process by separately reacting the RF with an alcohol (ROI-I) to produce the organic reactant ROR' and hydrogen fluoride. The organic reactant (ROR') is recovered from hydrogen fluoride by conventional methods for reuse, and the hydrogen fluoride may be used in making the difluoro phosphorus halide reactant. In the process of the present invention, the product organic phosphonyl difiuoride is obtained in a single reaction step. The difluoro phosphorus halide may be obtained from hydrogen fluoride without resorting to the use of elementary fluorine. For example, the following equations show a convenient method of 0btaining phosphorus trifluoride:

The reaction may be carried out in continuous or batchwise systems without departing from the scope of this invention. The reaction may also be effected in the presence of liquid diluents in which the reactants are dissolved or are dispersed, for example, as an emulsion.

The products of reaction are separated and recovered by conventional techniques. The organic phosphonyl difluoride may be recovered directly from the reaction mixture or it may be hydrolyzed to the corresponding phosphonic acids which may be then converted to various ester derivatives, or the phosphonyl difiuoride may be converted directly to a desired type ester or other derivatives by conventional methods and the derivatives recovered as the product of the process. The products are identified by the usual methods such as determination of boiling point and other such physical properties, determination of infra-red absorption analysis, percent composition analysis, and mass spectrometer analysis.

The following examples are offered as a better understanding of the present invention but the examples are not to be construed as unnecessarily limiting to the present invention.

Example 1 A 200 ml. steel pressure bomb is cooled in a Dry Ice acetone bath and is charged with 88 grams (1.0 mole) of phosphorous trifluoride and 46 grams (1.0 mole) of dimethyl ether. The bomb is then closed, placed in a reciprocating shaker and heated gradually to 250 C. and held at this temperature for 5 hours. The reaction is carried out under autogenous pressure, and under these reaction conditions it is estimated that the pressure obtained under equilibrium conditions is about 2800 p.s.i. absolute. After 5 hours of reaction, the bomb is cooled to about 0 C., and the pressure is released. The offgas contains some unreacted dimethyl ether and appreciable amounts of methyl fluoride. The residual liquid is then transferred to a distillation flask and distilled at atmospheric pressure to obtain a substantial amount of methane phosphonyl difiuoride. The reaction of. this example is illustrated by the following equation:

1s) v o CHr-O-CHs PF; CHIPi F 011;]?

Example 2 Example 3 A 200 m1. steel pressure bomb is cooled to a temperature of about C. and is charged with 89 grams (0.5 mole) of methyl acetate and 44 grams (0.5 mole) of phosphorous trifluoride. The bomb is then closed,

placed in a reciprocating shaker and heated gradually to 275 C. and held at this temperature for 7 hours After cooling to 0 C., the pressure is released and the reaction mixture is transferred to a distillation flask and distilled at atmospheric pressure. Methane phosphonyl difiuoride is isolated as the main product of reaction by distillation.

By employing the procedures similar to those of Examples 1-3, methane phosphonyl difiuoride also is obtained in substantial yield (i.e. in a yield of at least 5 percent) by interaction of phosphorus trifluoride with dimethyl sulfate, dimethyl acetal of acetone, and dimethyl acetal.

Although the above examples describe the preparation of methane phosphonyl difiuoride, other organic difluorides may be prepared similarly by the process of this invention. Thus, for example, when dibutyl ether is reacted with phosphorous trifiuoride at a temperature of about 275 C. at an elevated pressure of about 1500 p.s.i., butane phosphonyl difiuoride is obtained in substantial yield and is recovered as a product of the process. Further when about equimolar amounts of phosphorous trifluoride and ethyl propionate are interacted at a temperature of about 250 C. at an elevated pressure of about 1,000 p.s.i. for a time of about 5 hours, ethane phosphonyl difiuoride is produced in substantial yield and is recovered as a product of the process.

Although the invention has been described with relation to specific reaction conditions and operating techniques, various modifications and alterations may become apparent to those skilled in the art without departing from the scope of this invention.

Having described my invention I claim:

1. A process for the production of an organic phosphonyl difiuoride which comprises reacting a difluoro phosphorus halide with an organic compound of the formula ROR' where R is a radical having not more than 8 carbon atoms selected from the group consisting of an alkyl and a cycloalkyl radical and R is a radical having vnot more than 8 carbon atoms selected from the group consisting of an alkyl radical, a -CH O-alkyl radical, a

between about 200 C. and about 400 C. to produce an organic phosphonyl difiuoride of the formula T. and recovering said" organic phosphonyl difluoride. as a product of the'process:

2. The process of claim 1 in which said difluoro phos: phorus halide is difluoro phosphorous bromide.

3. The-process of claim 1" in which saiddifiuorophos phorus halide is difluoro-phosphorous chloride.

4. The process of claim 1 in which said difluoro phosphorus halide is phosphorus pentafluoride;

5. The-process of claim lin which saiddifluoro'phos-'- phorus halide is difluoro phosphorus trichloride.

6. A process for the production of an organic phosphonyl halide which comprises reactinga'phosphorus-trihalide containing two fluorine atoms with-a compound of the formula R-O-R' where R is an alkylradical having not more than eight carboniatoms and R' is a radical having not more than 8 carbon atoms selected from the group consistingof an alkyl radical, a'-CH ,O-alkyl radical, a;

-Blkyli radical, a

in; radical, and an SO O-alkyl radical, at atemperature between about 200 C. and about 400 C. toproduce an organic phosphonyl difluoride of. the formula R .F.Q. and recovering said organic phosphonyl. difluoride as a product of the process.

7. The process of claim 6 in which the reaction is effected in the presence of a Friedel-Crafts type catalyst.

8. The process of claim 6 in which the reactionis effected in the absence of a catalyst.

9. Avprocess for the production ofan organic PhOS? phonyl difluoride which comprises'reacting a phosphorus trihalide containing two fluorine atoms and in which the other halogen atom has an atomic weight not greater than. 80 witha compound of the formulaR-O-R? where R is an-alkyl radicalhaving not morethan eight carbon atoms and R is a radical having not more thanS carbon atoms. selected from the group consisting of an alkyl radical, a --CH O-a1kyl radical, a.

i -alky1' radical, a.

radical, and an -SO O-alky1 radical, at a temperature between about 200 C. and about 350 C. under liquid phase conditions to produce an organic phosphonyl halide of the formula R.i ?Faz and. recovering the organic phosphonyl halide thus produced as a product of the process.

10. A process for the production of a methane phos-- phonyl difluoride which comprises reacting a difluoro phosphorus halide in which the halogen atoms are those having an atomic weight not greater than 80 with an other of the formula CH -O-alkyl wherein the alkyl group has not more than 8 carbon atoms at a temperature of between about 200 C. and about 400 C. to produce a methane phosphonyl difluoride having the formula 0. (lHsr li and recovering the methane phosphonyldifluorid'e thus produced as a product of the process.

11. A process for the production of an organic phosphonyl'fl uoride' which comprises reacting a phosphorus trifluoride with an alkyl mono-ether in which each of the alkyl groupsbonded to theether oxygen has a continuous carbon skeleton of not more than eight carbon atoms, at a pressure between about 300 and about 3500 pounds per square inch and at a temperature of at least 200 C., to produce an organic phosphonyl fluoride in which the phosphorus is bonded to the carbon atom of an alkyl group having only a continuous carbon skeleton of not more than eight carbon atoms, and recovering said organic phosphonyl difluoride as a product of the process.

12. A process for the production of methane phosphonyl difluoride which comprises reacting a phosphorus fluoride with an organic compound of the formula CH O--R' where R is a radical having not more than 8 carbon atoms-selected fromthe group consisting of an alkyl radical, a -CH -O-alkyl radical, a

-alkyl radical, .a:

0 is radical, andan SO O-alkyl radical, at a temperature above 200 C. in the presence of a Friedel-Crafts catalyst to produce methane phosphonyl difluoride.

13. A process for the production of methane phosphonyl difluoride. which comprises reacting a phosphorous trihalide. containing two fluorine atoms and in which the other halogen atom has an atomic weight not greater than with dimethyl ether at a temperature between about 200 C. and about 350 C. to produce methane phosphonyl difluoride, and recovering the methane phosphonyl difluoride thus produced as a product of the process.

14. A process for the production of methane phosphonyl difluoride which comprises reacting phosphorous trifluoride with dimethyl ether at a temperature between about 200 C. and about 350 C. under autogenous con-' ditions such that methane phosphonyl difluoride is produced, and recovering the'methane phosphonyl difluoride as a product of the process.

15. The process of claim 14 in which the reaction is efllected in the presence of aluminum chloride as a catalyst.

16. A process for the production of methane phosphonyl difluoride which comprises reacting a difluoro phosphorus halide in which the halogen atoms are those havingan atomic weight not greater than 80 with an ester of the formula therefor O CH:- O-ii-alkyl inwhich the alkyl radical has not more than eight carbon atoms at a temperature between about 200 C. and about 400 C. to produce methane phosphonyl difluoride.

17. A process for the production of methane phosphonyl difluoride which comprises reacting a difluoro phosphorus halide in which the halogen atoms are those having an atomicweight not greater than 80 with methyl acetate at a temperature between about 200 C. and about 350 C. to produce methane phosphonyl difluoride and recovering the methane phosphonyl difluoride thus produced as a productof the process.

18. A process for the production of methane phosphonyl difluoride which comprises reacting a difluoro phosphorus halide in which the halogenatorns are those having an atomic weight not greater than 80 with dimethyl sulfate at a temperature between about 200 C. and about 350 C. to produce methane phosphonyl difluoride, and'recovering the methane phosphonyl difluoride thus produced as a product of the process.

19. A process for the production of methane phosphonyl difluoride which comprises reacting. a difluoro- 9 10 phosphorus halide in which the halogen atoms are those acetal at a temperature between about 200 C. and about having an atomic weight not greater than 80 with di- 350 C. to produce methane phosphonyl difluoride, and methoxy acetone at a temperature between about 200 C. recovering the methane phoiphonyl difluoride thus proand about 350 C. to produce methane phosphonyl diduced as aproduct of the process. fluoride, and recovering the methane phosphonyl difluoride 5 thus Produced as a product of the process References Cited in the file of this patent 20. A process for the production of methane phos- UNITED STATES PATENTS phonyl difluoride which comprises reacting a difluoro phos- 2,500,022 Brown Man 7, 1950 phorus halide in which the halogen atoms are those having an atomic weight not greater than 80 with dimethyl 

1. A PROCESS FOR THE PRODUCTION OF AN ORGANIC PHOSPHONYL DIFLUORIDE WHICH COMPRISES REACTING A DIFLUORO PHOSPHORUS HALIDE WITH AN ORGANIC COMPOUND OF THE FORMULA R-O-R'' WHERE R IS A RADICAL HAVING NOT MORE THAN 8 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF AN ALKYL AND A CYCLOALKYL RADICAL AND R'' IS A RADICAL HAVING NOT MORE THAN 8 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF AN ALKYL RADICAL, A -CH2-O-ALKYL RADICAL, A 